In industrial process measurements technology, especially also in connection with the automation of chemical processes or procedures for producing a product from a raw or starting material by the use of chemical, physical or biological processes and/or the automated control of industrial plants, electrical measuring devices installed near to the process, so called field devices, are applied, such as, for example, Coriolis mass flow measuring devices, density measuring devices, magneto-inductive flow measuring devices, vortex flow measuring devices, ultrasonic flow measuring devices, thermal, mass flow measuring devices, pressure measuring devices, fill level measuring devices, etc., which serve for producing measured values representing process variables, as well as measured value signals—in given cases also digital measured value signals—ultimately representing these measured values. The process variables in each case to be registered can be, depending on application, for example, mass flow, density, viscosity, fill level, limit level or the like, of a liquid, a powdered medium, a vaporous medium or a gaseous medium, which is conveyed or held in a corresponding container, e.g. a pipeline or a tank.
For registering the respective process variables, measuring devices of the aforementioned type contain, in each case, a corresponding physical to electrical, or chemical to electrical, measuring transducer. Such is most often inserted in a wall of the respective container containing the medium or into the course of a respective line—for example a pipeline—conveying the medium, and serves to produce at least one corresponding electrical measurement signal corresponding to the process variable to be registered. For processing the measurement signal, the measuring transducer is further connected with a measuring device internal, operating and evaluating circuit, which is provided in a measuring device electronics of the measuring device, and which serves for further processing or evaluation of the at least one measurement signal, as well as also for generating corresponding measured value signals. The latter, in the case of modern measuring devices of the type being discussed, is most often formed by means of a processor, such as, for instance, a microprocessor and/or a digital signal processor (DSP), clocked by a corresponding clock signal. Examples of such measuring devices or measuring transducers, and especially also details concerning their application and operation, are described in, among others, DE 100 41 166, DE-A 10 2005 032808, the DE-A 37 11 754n, DE-A 39 34 007, DE-A 44 12 388, EP-A 1 058 093, EP-A 1 147 463, EP-A 1 158 289, EP-A 1 197 732, EP-A 1 669 726, EP-A 525 920, EP-A 591 926, EP-A 866 318, EP-A 926 473, EP-A 984 248, US-A 2004/0117675, US-A 2005/0139015, US-A 2006/0096390, US-A 2006/0112774, US-A 2006/0120054, US-A 2006/0161359, US-A 2006/0179956, US-A 2007/0217091, US-A 2009/0000392, US-A 2009/0038406, US-A 2009/0277281, US-A 2010/0095784, US-A 2010/0236338, US-A 2010/0242623, US-A 2010/0242624, US-A 2010/0255796, U.S. Pat. No. 3,878,725, U.S. Pat. No. 4,308,754, U.S. Pat. No. 4,317,116, U.S. Pat. No. 4,468,971, U.S. Pat. No. 4,524,610, U.S. Pat. No. 4,574,328, U.S. Pat. No. 4,594,584, U.S. Pat. No. 4,617,607, U.S. Pat. No. 4,656,353, U.S. Pat. No. 4,716,770, U.S. Pat. No. 4,768,384, U.S. Pat. No. 4,777,833, U.S. Pat. No. 4,801,897, U.S. Pat. No. 4,850,213, U.S. Pat. No. 4,879,911, U.S. Pat. No. 4,926,340, U.S. Pat. No. 5,009,109, U.S. Pat. No. 5,024,104, U.S. Pat. No. 5,050,439, U.S. Pat. No. 5,052,230, U.S. Pat. No. 5,065,152, U.S. Pat. No. 5,068,592, U.S. Pat. No. 5,131,279, U.S. Pat. No. 5,207,101, U.S. Pat. No. 5,231,884, U.S. Pat. No. 5,359,881, U.S. Pat. No. 5,363,341, U.S. Pat. No. 5,416,723, U.S. Pat. No. 5,469,748, U.S. Pat. No. 5,535,243, U.S. Pat. No. 5,602,345, U.S. Pat. No. 5,604,685, U.S. Pat. No. 5,672,975, U.S. Pat. No. 5,687,100, U.S. Pat. No. 5,706,007, U.S. Pat. No. 5,731,527, U.S. Pat. No. 5,742,225, U.S. Pat. No. 5,742,225, U.S. Pat. No. 5,796,011, U.S. Pat. No. 5,804,741, U.S. Pat. No. 5,869,770, U.S. Pat. No. 5,959,372, U.S. Pat. No. 6,006,609, U.S. Pat. No. 6,014,100, U.S. Pat. No. 6,051,783, U.S. Pat. No. 6,073,495, U.S. Pat. No. 6,140,940, U.S. Pat. No. 6,236,322, U.S. Pat. No. 6,269,701, U.S. Pat. No. 6,285,094, U.S. Pat. No. 6,311,136, U.S. Pat. No. 6,352,000, U.S. Pat. No. 6,366,436, U.S. Pat. No. 6,397,683, U.S. Pat. No. 6,476,522, U.S. Pat. No. 6,480,131, U.S. Pat. No. 6,487,507, U.S. Pat. No. 6,512,358, U.S. Pat. No. 6,513,393, U.S. Pat. No. 6,535,161, U.S. Pat. No. 6,539,819, U.S. Pat. No. 6,556,447, U.S. Pat. No. 6,574,515, U.S. Pat. No. 6,577,989, U.S. Pat. No. 6,640,308, U.S. Pat. No. 6,662,120, U.S. Pat. No. 6,666,098, U.S. Pat. No. 6,769,301, U.S. Pat. No. 6,776,053, U.S. Pat. No. 6,799,476, U.S. Pat. No. 6,840,109, U.S. Pat. No. 6,854,055, U.S. Pat. No. 6,920,798, U.S. Pat. No. 7,017,424, U.S. Pat. No. 7,032,045, U.S. Pat. No. 7,073,396, U.S. Pat. No. 7,075,313, U.S. Pat. No. 7,133,727, U.S. Pat. No. 7,134,348, U.S. Pat. No. 7,200,503, U.S. Pat. No. 7,360,451, WO-A 00/14 485, WO-A 00/36 379, WO-A 00/48157, WO-A 01/02816, WO-A 02/086426, WO-A 02/103327, WO-A 02/45045, WO-A 03/048874, WO-A 2006/073388, WO-A 2008/003627, WO-A 2011/011255, WO-A 88/02 476, WO-A 88/02 853, or WO-A 95/16 897.
In the case of a large number of measuring devices of the type being discussed, for producing the measurement signal, the measuring transducer is driven during operation by a driver signal generated, at least at times, by the operating and evaluating circuit in such a manner that it acts, at least indirectly, or via a probe directly contacting the medium, practically directly, on the medium in a manner suitable for the measuring, on the medium, in order to bring about corresponding reactions there corresponding with the measured variable to be registered. The driver signal can, in such case, be correspondingly controlled as regards, for example, an electrical current level, a voltage level and/or a frequency. To be cited as examples for such active measuring transducers, that is measuring transducers correspondingly converting an electrical driver signal in the medium, are especially flow measuring transducers serving for measuring media at least at times flowing, e.g. measuring transducers with at least one coil operated by the driver signal and producing a magnetic field, or at least one ultrasonic transmitter driven by the driver signal, or also fill level and/or limit level transducers serving for measuring and/or monitoring fill levels in a container, such as, for example, measuring transducers with freely radiating microwave antennas, with Goubau lines or with vibrating immersion elements.
Devices of the type being discussed have, furthermore, at least one housing with at least one, usually pressure-tightly and/or explosion resistantly closed chamber accommodating electrical, electronic and/or electro-mechanical components and/or assemblies of the device, for example, components of the mentioned operating and evaluating circuit. Thus, for accommodating the measuring device electronics, measuring devices of the described type most often comprise a comparatively robust, especially impact-resistant, pressure-resistant, and/or weather-resistant electronics housing. This can be arranged—as, for example, provided in U.S. Pat. No. 6,397,683 or WO-A 00/36379—removed from the measuring device and connected with this only via a flexible line; it can, however—as is shown, for example, in EP-A 903 651 or EP-A 1 008 836—also be arranged directly on the measuring transducer or on a transducer measuring transducer housing separately housing the measuring transducer. In given cases, the electronics housing can then, as is, for example, shown in EP-A 984 248, U.S. Pat. No. 4,594,584, U.S. Pat. No. 4,716,770 or U.S. Pat. No. 6,352,000, also serve to accommodate some mechanical components of the measuring transducer, such as, for example, membrane, rod, sleeve or tubular deformation or vibrating elements operationally deforming under mechanical action; compare for this also the previously mentioned U.S. Pat. No. 6,352,000 or U.S. Pat. No. 6,051,783.
In the case of measuring devices, the respective measuring device electronics is usually electrically connected via corresponding electrical lines to a superordinated electronic data processing system arranged most often spatially removed from the respective device and most often also spatially distributed, wherein measured values produced by the respective measuring device are promptly forwarded to this data processing system by means of a measured value signal correspondingly carrying these measured values. Electrical devices of the described type are additionally usually connected by means of a data transmission network provided within the superordinated data processing system with one another and/or with corresponding electronic process controllers, for example, programmable logic controllers, installed on-site or process control computers installed in a remote control room, to which the measured values produced by means of the measuring device and digitized and correspondingly suitably encoded are forwarded. By means of such process control computers, the transmitted measured values can be further processed and visualized as corresponding measurement results, e.g. on monitors, and/or be converted into control signals for other field devices embodied as actuating devices, e.g. magnetic valves, electric motors etc. Since modern measuring arrangements most often can also be directly monitored and, in given cases, controlled and/or can be configured by such control computers, associated operating data are in a corresponding manner likewise sent to the measuring device via the aforementioned transmission networks, which are most often data transmission networks that are hybrid as regards the transmission physics and/or the transmission logic. Accordingly, the data processing system usually also serves to condition—for example, to suitably digitize—the measured value signal delivered by the measuring device corresponding to the requirements of downstream data transmission networks, and, in given cases, to convert the signal into a corresponding telegram, and/or to evaluate it on-site. For such purpose, in such data processing systems, evaluating circuits electrically coupled with the respective connecting lines are provided, which pre-process and/or further process as well as, if required, suitably convert the measured values received from the respective measuring and/or switching device. Serving at least sectionally for data transmission in such industrial data processing systems are fieldbusses, especially serial fieldbusses, such as, for example, FOUNDATION FIELDBUS, RACKBUS-RS 485, PROFIBUS, etc., or, for example, also networks based on the ETHERNET standard, as well as the corresponding, most often comprehensively standardized, transmission protocols.
Besides the evaluating circuits required for processing and converting the measured values delivered by the respectively connected measuring devices, such superordinated data processing systems most often also have electrical supply circuits serving for supplying the connected measuring and/or switching devices with electrical energy. Thus, such electrical supply circuits provide corresponding supply voltages (in given cases fed directly by the connected fieldbus) for the respective measuring device electronics, and drive the electrical currents flowing through the electrical lines connected thereto as well as through the respective measuring device electronics. In such case, a supply circuit can be associated, for example, in each case, with exactly one measuring device, and, together with the evaluating circuit associated with the respective measuring device—for example, united to form a corresponding fieldbus adapter—be accommodated in a shared electronics housing, embodied, for example, as a hatrail module. It is, however, also quite usual to accommodate supply circuits and evaluating circuits in each case in separate electronics housings, in given cases spatially remote from one another, and correspondingly to wire these with one another via external lines.
As mentioned, among others, in the previously mentioned EP-A 1 197 732 or US-A 2009/0000392, measuring devices of the type being discussed, are at times to be tested—be it at the instigation of the user operating the measuring device and/or due to a requirement of one of the authorities overseeing the measuring point formed by means of the measuring device—as to whether the required accuracy of measurement or that stated in the specification is still reliably achieved, or whether the measuring device—for instance, as a result of wear of the measuring transducer and/or aging of the measuring device electronics—no longer measures sufficiently precisely or no longer in a sufficiently reproducible manner.
Such tests of the measuring device electronics in the context of a subsequent verification of its measuring functionality, or an equally subsequent validation of the measured values produced by means of the measuring device regularly occurs in the case of conventional measuring devices by a correspondingly certified external testing device being connected to the measuring device electronics via a service interface, wherein the external testing device serves to apply at least one defined test signal corresponding to the at least one measurement signal at the input of the measuring device electronics for the respective measurement signal of the measuring transducer. By means of the test signal, a particular behavior of the measuring transducer, and consequently a corresponding particular measured value for the measured variable otherwise to be registered can thus in each case be simulated. In association therewith, by means of the measuring device electronics, the test measured values corresponding with the respective test signal can thus be produced and compared with specifications for test measured values corresponding with the respective test signal. If the test measured values deviate by less than an allowable highest tolerance from the specifications, the measuring device electronics and consequently the measuring device has then passed these tests, and consequently, the measuring device electronics is correspondingly verified and permitted for further operation.
A disadvantage of such a method for testing measuring device electronics is particularly to be seen in the fact that, for its performance, normal measuring operation of the measuring device must be interrupted, and consequently the portion of the plant monitored from the measuring point must be taken out of operation for the duration of the test. Moreover, such testing requires a special, most often very expensive, testing device, which recurringly must undergo very complex recalibration. Furthermore, this kind of testing is regularly performed only by correspondingly trained and permitted examiners.